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Alpa's HPF rings

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photohagen

Guest
let's assume i shimmed my db and also installed the ring properly as per instructions. how accurate is the distance scale on these hpf rings especially at closer distances? can i use a laser distance meter, dial up the distance on the ring, and get accurate focus?

richard
 

Thierry

New member
Yes Richard, Graham is right and of course it is then a 100% accurate.

As a reminder, here you can get the detailed information how the shimming works and is done, and why it is so important.

Alpa adjustable back adapter

Best regards
Thierry

let's assume i shimmed my db and also installed the ring properly as per instructions. how accurate is the distance scale on these hpf rings especially at closer distances? can i use a laser distance meter, dial up the distance on the ring, and get accurate focus?

richard
 

danlindberg

Well-known member
Yes, it is very precise indeed. I was a little hesitant in the beginning but can also confirm that the combination Disto 5 and HPF rings on a correctly calibrated Alpa is totally reliable.
 

dougpeterson

Workshop Member
Thierry, pet peeve of mine, often irked by companies like Alpa. Can you please say it's "extremely accurate" or such? Nothing is ever 100% accurate.

This reminds me of when it was claimed pre-launch the S2 would "not moire" (the qualitative version of "100%"). Engineering wise everything will moire in the right situation. Engineering wise nothing is 100% accurate.

The S2 is a great camera and the HPF are a great tool. Like I said, just a pet peeve.
 

Guy Mancuso

Administrator, Instructor
I have one for my 90 on the way. Along with a Disto 5 as well.

BTW Paul at Optechs got a bunch in.
 

Guy Mancuso

Administrator, Instructor
I would love one for my 60 but with my Tilt Swing knobs i would need a custom adjustment to my lens knobs. Thierry I wonder if they could make one without the focusing knobs not the screw in pins but without the whole focus ring around the HPF and make it thinner. I know major tooling but be interesting to hear what they had to say about it.
 

Thierry

New member
Doug, why "irked by Alpa"?

Fact is that one can focus exactly where one wants the focus to be, and not meters or 1/10s of a meter behind or in front, WHEN the digital back is shimmed precisely, with exactly precision needed when focusing, not more but also not less.

Is that a better way to say it or still too much?

;)

Best regards
Thierry

Thierry, pet peeve of mine, often irked by companies like Alpa. Can you please say it's "extremely accurate" or such? Nothing is ever 100% accurate.

This reminds me of when it was claimed pre-launch the S2 would "not moire" (the qualitative version of "100%"). Engineering wise everything will moire in the right situation. Engineering wise nothing is 100% accurate.

The S2 is a great camera and the HPF are a great tool. Like I said, just a pet peeve.
 

GrahamWelland

Subscriber & Workshop Member
Fact is that one can focus exactly where one wants the focus to be, and not meters or 1/10s of a meter behind or in front, WHEN the digital back is shimmed precisely, with exactly precision needed when focusing, not more but also not less.
In all fairness it's probably also worth adding that so long as the back is shimmed, AND the HPF ring is aligned correctly with the lens infinity mark then you'll have a very accurate match of focus distance to distance on the HPF ring. Aligning the HPF ring with the helicoid isn't difficult but with wide lenses even a very minor misalignment would result in things being off vs a distometer reading.
 
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photohagen

Guest
an important variable not mentioned: where do you line up the laser to take a measurement? i assume it's parallel to the sensor. and if so, approximating where the sensor is located each and every time can be less than 100% accurate.

rh
 

Thierry

New member
That's of course correct, Graham.

AND, to be complete, with calibrated lenses to be able to have precision with ALL used lenses.

Thierry

In all fairness it's probably also worth adding that so long as the back is shimmed, AND the HPF ring is aligned correctly with the lens infinity mark then you'll have a very accurate match of focus distance to distance on the HPF ring. Aligning the HPF ring with the helicoid isn't difficult but with wide lenses even a very minor misalignment would result in things being off vs a distometer reading.
 

Thierry

New member
Dear Guy,

I don't think Alpa is going to produce accessories for other brands.

Best regards
Thierry

I would love one for my 60 but with my Tilt Swing knobs i would need a custom adjustment to my lens knobs. Thierry I wonder if they could make one without the focusing knobs not the screw in pins but without the whole focus ring around the HPF and make it thinner. I know major tooling but be interesting to hear what they had to say about it.
 

dchew

Well-known member
For me, the HPF/D5 is not only accurate, but also the most efficient way to focus. I know some, including Jack I think, have had success using live view on the IQ back. I still struggle with live view for focusing, but I admit I haven't given it the full College Try.

If the subject is relatively close you can flip down the little corner foot on the D5, then position the D5 right on top of the camera with the foot up against the back of the camera. Makes it fairly stable without the need for mounting the D5 onto the camera. If you are really anal - sorry precise - you can add a zero adjustment to the D5 to add a small amount that accounts for the difference between wherever you set the base of the D5 and where the sensor plane is. But for my setup it is only like 0.02 feet / 0.0061m (yes, the D5 can go out 4 dec places in meters!).

I THINK the D5 is the only real effective option that works well for this application. The video feature makes all the difference.

Dave
 

dchew

Well-known member
you can also set the D5 to display ft-decimal ft, to match the HPR ring markings
Yeah, that's how I have mine set, 0.00 ft to match the foot-scale HPF rings I have.

I debated which HPF rings to order, since 0.00 feet is more accurate than 0.00 meters. But if you look at the HPF distance tables it turns out to be almost a wash. The tables are in three significant digits, i.e. x.xx until less than 1 meter or foot, where they switch to 0.xxx. So at just under 1 meter you get 0.999 in meters but still 3.28 feet. Once you get under a foot, which is almost never for me, do you get the third decimal on the ft scale. Too much thinking to matter!
:rolleyes:

Dave
 
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photohagen

Guest
i am no longer skeptical. i received my hpf ring yesterday. installed it and tested it today. every setting from my laser to my ring gave me perfect focus.

thanks to everyone for their input. merry christmas!

rh
 
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